If they are Oasis, I assume they are the florist foam cubes used often for
cuttings. I also grow a couple thousand seedlings each spring in my
greenhouse and I've tried just about every growing medium. I used some
oasis cubes for impatiens one year and was not happy with the results. It
seemed to me that the foam constricted the growth of the plant's stem at
its base/"ground level". I believe oasis cubes/wedges are used much more
often now in commercial operations, so the product may have been improved.
I would guess you would have to pay more attention to fertilizer using such
an inert medium. I will be very interested to hear your results; please
keep us posted.